Method and system in control of coating color recipe

ABSTRACT

The amount of at least one coating mix component and/or the ratios of two or more components are measured by a measuring device arranged in conjunction with the coating mix. The measurement is taken from finished coating mix and/or coating mix to be recycled for use in the manufacture of new coating mix. On the basis of the measurement result the ratios and/or amount of the components fed into the coating mix to be manufactured and/or recycled are controlled.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a U.S. National Stage application of InternationalApplication No. PCT/FI02/00324, and claims priority on FinnishApplication No. FI 20010818, Filed Apr. 20, 2001.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The invention relates to a method and system in control of a coatingColor recipe.

The chemical composition of coating mix in manufacture, that is, forexample its pigment, binder and thickener composition and the amount ofother additives, are determined on the basis of a coating Color recipe.The coating Color recipe determines the amounts and/or ratios of thevarious components of the coating mix. According to the Color coatingrecipe, the coating mix may contain, for example, 50 parts calciumcarbonate, 50 parts kaolin, 10 parts latex and 0.1 parts lye, that is,the sum of the ratio of the components may be greater than 100. Controlof the coating Color recipe in this connection refers to measures, whosepurpose is to produce a new coating mix complying with the coating Colorrecipe, or to make a partly recycled coating mix as close as possible tothe coating mix according to the coating Color recipe.

In the manufacture of coating mix, recycled mix, that is, for example,coating mix collected from the machine cycle, or recovered mix, is usedas one component to reduce manufacturing costs. Concentrate, that is,mix recovered by filtering (for example by means of an ultrafilter ornanofilter) from collected waters containing coating, is also often usedin coating mix manufacture. In addition, in coating change, that is, inconnection with changing the coating Color recipe, the aim is to recoverthe old coating. Recovery takes place partly by pumping the coating mixfrom the machine cycle to a recovery tank. Coating mix is also conveyedto the recovery tank partly along with the washing waters. The drymatter content of the fraction obtained through recovery by these twomethods may vary considerably, being typically between 0.5–65%. Thecollection methods and different methods for treating the fractions alsocause chemical changes in the properties of the coating. For example, inultrafiltration, small-molecule components, such as, for example, thedextrines of the starch contained in the coating mix, pass through thefilter with the water, whereby the structure of the coating mix changesas the amount of small-molecule components changes.

The properties of the mix in the machine cycle are known to change inconnection with the coating process. The changes are caused, among otherthings, by the migration of binder, water, optical brightener and othercomponents to the base paper. Some of the changes are also due to theevaporation of water when the coating is in contact with air, forexample, in the return trough and on the surface of the machine chest.The water balance of the machine cycle may also change due to the effectof external factors, such as, for example, cleaning showers andcondensate waters.

Due to the effect among other things, of the changes and uncertaintyfactors described above, in known solutions the concentrate is typicallyalmost always treated in terms of the calculation as a pigment. However,in addition to pigment, the concentrate also contains many othercomponents, such as latex. If the chemical composition of theconcentrate, that is, the amount of components contained in it, or theirratio, were known, then for example in coating mix manufacture, theamount of latex could be reduced, which would result in considerablecost savings.

Furthermore, changes in the properties of coating mix affect the qualityof the final coating and the runnability of the coating process. Thus,for example, a decrease in the amount of thickener and latex willincrease the viscosity of the coating mix, which will have a significanteffect on the runnability of the coating process. Furthermore, it isalso known that using concentrate in the manufacture of coating mix willdecrease the viscosity of the finished coating mix.

Thus a need has arisen to measure the properties of coating mix in themachine cycle and during coating mix recovery. There has also arisen aneed to control the properties of the coating mix to be made on thebasis of the properties of the coating mix when ready and when used forcoating.

European patent application EP 0 962 769 discloses a method and anapparatus for measuring the properties of a composition or componentused in paper or board manufacture. According to the application, asample taken of the composition is measured for dry matter content,viscosity and pH. A problem with the solution presented in theapplication is that it does not reveal the chemical composition of thecomposition. Thus, for example, the real cause of a change in viscosityof the composition cannot be discovered, which means that it isdifficult to so remedy the problem effectively and efficiently.

Furthermore, for example, from the patent application WO 99/14579 thereis known a method and device for measuring the properties of paper bydirecting an infrared beam onto the surface of a moving paper web. Abeam that has passed through or been reflected from the web is dividedinto wavelength components by means of a spectrograph and the signalsare measured for the various wavelength components, on the basis ofwhich signals the properties of the paper are determined. Theapplication does not, however, disclose the use of the measurementresults in the control and/or regulation of coating mix manufacture.

Patent application WO 99/41590 discloses a method and device formeasuring the amount of coating on a moving substrate based onreflection measurement. In accordance with the publication, the amountof calcium carbonate is measured by measuring the absorption peak ofcalcium carbonate in the wavelength range, which is approximately 3.95micrometers and/or the amount of kaolin is measured by measuring theabsorption peak of kaolin in the wavelength range, which isapproximately 2.7 micrometers. According to the publication, themeasurement results are used for determining the thickness of thecoating and not for controlling or regulating coating manufacture.

In addition, Pentti Niemelä and Janne Suhonen have, in their article “AnIndustrial Raman Spectrometer for Process Measurement Applications”,presented a measuring device based on Raman spectroscopy for measuringthe chemical properties of matter.

SUMMARY OF THE INVENTION

In the present invention it has been recognized that by measuring theproperties of coating mix and/or the recyclable mix used for coating mixmanufacture, the coating mix and its manufacture, especially the coatingColor recipe, can be controlled and managed efficiently.

The aim of the method and system relating to the present invention is,therefore, to eliminate, or at least substantially reduce the problemsdue to the above-mentioned prior art, and to provide a method and systemin the control of coating mix, by means of which the chemicalcomposition of coating mix can be reliably determined, and whichcomposition data will be used in the manufacture of coating mix.

Another aim of the method and system relating to the present inventionis to make possible the manufacture of a new coating mix by utilizingrecycled coating mix as efficiently as possible.

A further aim of the present invention is to attempt to predict changestaking place in the coating mix, such as changes in viscosity or waterretention.

In a typical method according to the invention, measurement is takenfrom finished coating mix and/or recycled coating mix used for themanufacture of new coating mix. Finished coating mix in this connectionrefers to both coating mix discharged from a mixer used for mixing thecomponents in coating mix manufacture, which coating mix is thenconveyed to the coating apparatus either directly or via one or morecontainers, and coating mix already applied to the surface of thematerial. On the basis of the result of measurement carried out in thisway, the ratios and/or amount of the components fed into the coating mixto be manufactured and/or recycled are controlled. In a preferred methodaccording to the invention, the amounts and/or ratios of componentsobtained as measurement results are compared with the amounts and/orratios according to the recipe for the coating mix to be made, andcontrol of the ratios and/or amount of the components fed into thecoating mix to be made and/or recycled is carried out on the basis ofthe said comparison. In this connection, the recipe for the coating mixto be made refers to the amount and/or ratio of the coating mixcomponents when the coating mix is made completely of new components.

In a preferred method according to the invention, measurement is carriedout on the machine cycle. The measuring device used in the method isthen connected either directly to the coating mix transfer line or to aseparate sampling line, to which the coating mix is conveyed from themachine cycle. Furthermore, the measurement is most preferably carriedout essentially continuously. When measurement is carried out on themachine cycle, no separate sampling and sample transfer, for example, toa laboratory, are required, which makes measurement faster and morereliable. In this case, in addition, an on-line type measuring methodcan be realized, which method measures the properties of the coating mixcontinuously or at desired intervals.

In one most preferable method relating to the invention, the amount ofbinder and/or thickener contained in the coating mix is measured fromthe coating mix. In this case, changes in the properties of the coatingmix can be predicted particularly well, and the amount of binder orthickener can be increased or decreased if necessary. Most preferably,the amount of binder and/or thickener can be measured by comparing theirratio, for example, to the pigment.

In the method according to the invention, for example, NIR-, MIR-, IR-or Raman-spectroscopy can be used as a measuring method, or anothermethod by means of which the chemical properties of a substance can bemeasured and/or determined.

A typical system according to the present invention comprises at leastmeans for taking measurements from finished coating mix and/or thecoating mix to be recycled for making new coating mix, and means forcontrolling on the basis of the measurement result the ratios and/oramount of the components fed into the coating mix to be made and/orrecycled. A preferred system according to the invention also comprisesmeans for comparing the amounts and/or ratios of components obtained asa result of the measurement with the amounts and/or ratios according tothe coating mix recipe, and means for controlling the ratios and/oramount of the components fed into the coating mix to be made and/orrecycled on the basis of the above comparison.

The system may also be implemented in a preferred manner in such a waythat the means for measuring the amount of at least one component or theratio of one or more components from the coating mix are mounted on thecoating mix transfer line. In another preferred system according to theinvention, the means for measuring the amount of at least one componentor the ratio of one or more components from the coating mix are mountedon the container containing coating mix. When the above-mentioned meansare located directly on the coating mix transfer line and/or thecontainer containing coating mix, it is ensured that the object ofmeasurement is a sample representing the true state of the coating mix.

The system according to the present invention may also be realized in apreferred manner in such a way that the means for measuring the amountof at least one component or the ratio of one or more components areconnected to the coating mix transfer line and/or the containercontaining coating mix on one or more sampling lines. By means of thesampling lines, the system can be moved to a location preferable fromthe point of view of the usability of the system, such as installationor maintenance. Furthermore, by bringing the coating mix to be measuredfrom several points to one place, one measuring device of the systemaccording to the invention can be used for measurement at severalmeasuring points.

Typically, the method according to the invention is implemented by meansof a computer software product that can be directly loaded into the mainmemory of the computer, or by means of a computer software product thatis stored on a computer-readable medium, the computer software productcontaining the program code elements required for implementing themethod according to the invention when the said computer softwareproduct is run in the computer. A computer software product in thisconnection refers to independent computer software or part of computersoftware, which may comprise one or more program code elements. Aprogram code element refers to an element consisting of one or moreinstructions or commands in computer-readable form. A computer-readablemedium in this connection refers to all such media in which data,instructions, commands, series of instructions or commands or the like,which are computer-readable, can be stored permanently or temporarily.Such media are, for example, fixed discs, mass memories, bufferstorages, disks and CD-ROMs.

One typical above-mentioned computer software product, which is storedon a computer-readable medium, comprises at least the following programcode elements:

a program code element making it possible for the computer to receivemeasurement data from one or more measuring devices measuring coatingmix properties,

a program code element enabling the computer to compare the propertiesof the coating mix based on measurement data with the target properties,and

a program code element for enabling the computer to control the feed ofthe coating mix components in the manufacture of coating mix when thecomputer software product is run in a computer.

By means of the computer software product, the method according to theinvention for controlling the coating mix can be used in a computer oras a part of another device, which comprises the means for running thecomputer software product in such a way that the method according to theinvention can be automated by means of it.

One preferred computer software product according to the inventionadditionally comprises a program code element for enabling the computerto store—preferably in a database—data on the target properties of oneor more coating mixes. The above-mentioned program code element thusmakes it possible to use the method for measuring several differentcoating mix types.

One preferred computer software product according to the inventioncomprises a program code element for enabling the computer to store in adatabase at least the measurement data it has received and/or comparisondata on the properties of the coating mix obtained on the basis ofmeasurement data compared to the target properties. Thanks to theabove-mentioned program code element, a database can be obtained, fromwhich, for example, the behavior of the coating mix as a function oftime can easily be monitored.

The greatest advantage of the present invention is that by measuring theamount of thickener and binder contained in the coating to be recycled,the recipe for preparing fresh coating mix can be changed in such a waythat the amounts of binder and thickener in the finished coating mixremain constant irrespective of whether concentrate is used in therecipe or not. This results in considerable cost savings, since theamount of the components incurring the greatest costs can be reduced inmanufacture by utilizing the components contained in the recyclablecoating mix as efficiently as possible.

A further advantage of the present invention is that when the propertiesof the coating mix to be recycled, such as binder content, etc. areknown, it is easy to predict the amount of binder needed in coating mixmanufacture for the fresh coating. The final amount of binder can, in apreferred case, be checked by the same method that is used for measuringthe properties of recyclable coating.

Furthermore, by means of the method and system according to the presentinvention, the properties of the coating mix can be kept more stablethan before, whereby the runnability of the coating station will improveand there will be fewer interruptions caused by coating.

The invention is described in greater detail in the following, withreference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows diagrammatically the system relating to the invention aspart of the machine cycle.

FIG. 2 shows diagrammatically a second example of the location of themeasuring device used in the system as part of the machine cycle.

FIG. 3 shows an example of an application of the method according to theinvention as a flow chart.

FIG. 4 shows, by way of an example, a measurement result of the methodrelating to the invention.

FIG. 5 shows, by way of an example, a measurement result of the methodrelating to the invention on the base line.

FIG. 6 shows, by way of an example, a measurement result base linecorrected of the method relating to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows diagrammatically and by way of an example the systemaccording to the present invention when mounted as part of a machinecycle.

Of the machine cycle, FIG. 1 shows, for example, a recovery tank 1 forwashing waters recovered from the coating station. From the washingwater recovery tank 1, the washing water containing coating mix isconveyed to an ultrafilter 2, from where the reject, that is,concentrate is conveyed to a concentrate tank 3. The permeate, that is,the water contained in the washing water, can be conveyed to a channeland from there further to a purification plant, or it may be utilizedelsewhere in the paper manufacturing process. Further, of the machinecycle is shown a residual mix tank 4 for residual mix, that is, forexample, coating mix recovered from the coating machine or mix kitchens,a mixer 5 and a coating station tank 6. The pipes acting as transferlines are marked with reference numeral 7. The machine cycle alsocomprises many other devices and parts, such as various pumps andvalves, which are not shown in FIG. 1 in order to simplify the Figure.For example, many other components 12 are typically also conveyed to themixer 5, such components as, for example, carbonate, kaolin, latex, CMC(carboxymethylcellulose), thickener and optical brightener.

Alternative and illustrative locations for the measuring device used inthe system are marked with reference numerals 8 a–8 d. Reference numeral8 a shows a measuring device mounted on the transfer line between theconcentrate tank 3 and the mixer 5. Reference numeral 8 b refers to ameasuring device located between the residual mix tank 4 and the mixer5. Under reference numeral 8 c is shown a measuring device, which islocated between the mixer and the coating station tank and thus used formeasuring the finished coating mix. The measuring device located in thecoating station tank 6 is marked with reference numeral 8 d. Themeasuring device 8 d located in the coating station tank can be replacedby conveying coating mix from the coating station tank by a separatesample line 9, for example, to the measuring device 8 c, as shown inFIG. 1.

FIG. 2 shows diagrammatically and by way of an example, anotheralternative solution for locating the measuring device used in thesystem according to the invention. According to FIG. 2, the measuringdevice 10 is connected to the transfer lines 7 by means of the samplelines 9, along which a sample of the concentrate, residual mix andfinished coating mix is conveyed to be measured. The measuring device 10is implemented in such a way that it has means for synchronizingsampling, which means that it is possible to take measurements from thedesired transfer line at desired intervals. The measured sample can bereturned to the transfer fine or it may be conveyed, for example, to theresidual mix tank (handling of the measured sample is not shown in theFigure).

In the system according to the invention all the measuring devices shownin FIGS. 1 and 2 are not necessarily needed, but the number andlocations of the measuring devices are determined according to therespective needs concerning measurement or use. In addition, the systemmay be implemented by using measuring devices installed directly on thetransfer line or container, or by means of sample lines and any samplecontainers used.

The type and structure of the measuring devices shown in FIGS. 1 and 2will depend on the method used for measurement. One measuring deviceapplicable to the system is disclosed in the above-mentioned publication“An Industrial Raman Spectrometer for Process Measurement Applications.”

In accordance with what is shown in FIGS. 1 and 2, the measuring devices8 a–8 d and 10 are connected in a manner known as such to a control unit11 controlling the manufacture of the coating mix in order to transmitthe measurement data from the measuring devices to the said controlunit. The measurement data transferred may be final measurement resultson the amounts and/or ratios of components. The calculation of themeasurement results can also be implemented in such a way that resultcalculation and/or analysis is carried out partly or completely in thecontrol unit 11. The control unit compares the measurement resultobtained with the base line of the recipe for the coating mix to be madeand determines the difference between these. The amount of components inthe coating mix to be made or their ratio to each other is determined onthe basis of the difference obtained or the ratio calculated from thedifference. The system may also comprise other means than the above,such as a computer for calculating or analyzing the results. On thebasis of the measurements made by the measuring devices, the controlunit 11 controls, for example, the feed of components 12 into the mixer5 in a manner known as such, taking into account the amounts and/orratios of components contained in the concentrate and/or residual mix.

The method and system relating to the present invention may also beimplemented in such a way that the properties of the finished coatingmix are measured from the surface of a material web coated with coatingmix, for example, by means of reflection measurement, and this result isused alone or together with other measurements for controlling and/orregulating the manufacture of the coating mix to be made.

FIG. 3 shows one example of an application of the method according tothe invention as a flow chart. The coating mix or concentrate ismeasured by means of a measuring device mounted in conjunction with themachine cycle, for example, using Raman-spectroscopy. After this, asample curve of the measurement signal is drawn. The sample curve iscompared with the base line according to the coating mix recipe to bemeasured and the difference between the coating mix to be measured andthe recipe is determined. On the basis of the difference obtained, theamount and/or ratios of the components fed into the coating mix to bemade or recycled is controlled, for example, by decreasing or increasingthe amount of one or more of the coating mix components. If, forexample, concentrate with a high latex content is used as one of the rawmaterials in the manufacture of the new coating mix, the amount of latexfed during manufacture can be reduced compared with the amount accordingto the coating mix recipe by the amount of latex contained in theconcentrate. In this way cost savings are achieved as the consumption oflatex decreases. In accordance with the above, measurements based onother than Raman-spectroscopy can also be used in determining theamounts and/or ratios of coating mix components.

FIGS. 4 to 6 show by way of an example a measurement result for twocoating mixes, the first of which contains six parts latex and thesecond nine parts latex. A measuring apparatus and method based onRaman-spectroscopy is used in the measurement. The vertical axis in theFigures shows intensity and the horizontal axis shows Raman shift.

FIG. 4 shows the measurement result given by the measuring device, thatis, the Raman-spectra for the above-mentioned coating mix samples. InFIG. 5, base line corrections have been made to the spectra of FIG. 4.The base lines are shown by broken lines in FIG. 5. In FIG. 6 thespectra are moved to the base line. The Figures show peaks in differentwavelength ranges, which indicate a difference in the amounts and ratiosof the components in the samples. By comparing these peaks and/or theirranges with the base line, the ratio of the components and/or the amountof one or more components contained in the sample can be calculated.After this, the result of the calculation may be utilized in accordancewith the present invention for controlling and/or regulating coating mixmanufacture.

The aim has not been to limit the invention only to the embodimentsdisclosed in the previous specification, but it may be varied within thescope of the inventive idea presented in the claims.

1. A method in control of composition of a coating color mix comprising the steps of: recovering a coating color concentrate from washing water containing coating color mix or recovering coating color residuals from a coating machine or from mix kitchens; combining in a mixer a plurality of coating components including at least a thickener and a binder, and the coating color concentrate from the washing water mix, or the coating color residuals, to thus form a finished coating color mix; measuring the finished coating color mix to determine at least one property selected from the group consisting of: amount of thickener in the coating color mix, a ratio of the thickener to another component of the coating color mix, amount of binder in the coating color mix, and a ratio of the binder to another component; and on the basis of the at least one selected property measured in the finished coating color mix controlling the amount of at least one component added to the mixer in the combining step to form the finished coating color mix.
 2. The method of claim 1, wherein the component forming the ratio with the thickener is pigment.
 3. The method of claim 1, wherein the component forming the ratio with the binder is pigment.
 4. The method of claim 1, wherein the at least one property controlled is controlled to match a recipe for a coating color mix to be made.
 5. The method of claim 1, wherein the measurement is carried out between components of a machine cycle, said components including a coating mixer, a concentration tank, a residual mix tank and a coating station tank.
 6. The method of claim 1, wherein the steps of measuring the amount of thickener and measuring the amount of binder are carried out essentially continuously.
 7. The method of claim 1, wherein the measuring is carried out by NIR-spectroscopy, MIR-spectroscopy, IR-spectroscopy or Raman-spectroscopy.
 8. A system for control of a coating color mix, of the type having: a means for conveying the coating color mix to at least one measuring point; a measuring system that comprises means for measuring the amount of at least one component or the ratio of two or more components from the coating color mix; the improvement comprising: a means for receiving recycled coating color mix from a coating machine; a means for taking measurements of the recycled coating color mix used in manufacture of new coating color mix; and a means for controlling on the basis of the measurement result the ratios and/or amount of components fed into the coating color mix to be made and/or recycled.
 9. The system of claim 8, wherein the system comprises means for comparing the amount and/or ratios of components obtained as a result of the measurement with the amounts and/or ratios according to a coating color mix recipe, and means for controlling on the basis of the above comparison the ratios and/or amount of the components fed into the coating color mix to be made and/or recycled.
 10. The system of claim 8, wherein the means for measuring the amount of at least one component or the ratio of two or more components from the coating color mix are fitted in a coating color mix transfer line.
 11. The system of claim 8, wherein the means for measuring the amount of at least one component or the ratio of two or more components from the coating color mix are fitted in a container containing coating color mix.
 12. The system of claim 8, wherein the means for measuring the amount of at least one component or the ratio of two or more components from the coating color mix are connected to a coating color mix transfer line and/or a container containing coating color mix on at least one sampling line.
 13. A method of controlling and applying a coating color mix containing thickener, binder, and pigment, which is applied to a paper web or board web, comprising the steps of: forming a coating color mix from recycled coating color and recovered coating color and other components; measuring the ratio of the thickener to pigment in the coating color mix; measuring the ratio of the binder to pigment in the coating color mix; and controlling the ratios of thickener to pigment, and binder to pigment, based on the measured ratio of thickener to pigment, and the measured ratio of binder to pigment.
 14. A method in control of composition of a coating color mix, the method comprising the steps of: recovering a coating color concentrate from washing water containing coating color mix or recovering coating color residuals from a coating machine or from mix kitchens; combining in a mixer a plurality of coating components, including at least a thickener and a binder and either the coating color concentrate from the washing water mix or the coating color residuals, to thus form a finished coating color mix; measuring the coating color concentrate or recovered coating color residuals to determine at least one property; and on the basis of the at least one determined property, controlling the amount of at least one component added to the mixer in the combining step to form the finished coating color mix. 